Floral development in Caulophyllum thalictroides (Berberidaceae)

Abstract

A study of floral development in Caulophyllum thalictroides led to a reevaluation of the structure of the flower. After the production of sepal primordia, common stamen–nectary primordia arise. Nectary primordia are produced abaxially as a result of bifurcations of the common stamen–nectary primordia. The nectaries therefore cannot be considered reduced petals as traditionally interpreted and are perhaps better regarded as staminal derivatives. Three whorls of sepals develop; the lowermost often being dimerous, while the upper two whorls are more typically trimerous. The interpretation of the lowermost whorl of sepals as bracts was questioned. The terminology with regards to the inflorescence was considered, and after examination of material from this taxon it was felt that the inflorescence is best described as a cymosely branched panicle.